(1) Field of the Invention
The invention relates to a securing unit for use in mounting at least two printed circuit boards and for holding the boards in different holding states such as a closed state in which the boards are adjacent and parallel and an open state in which one board is moved away and held at an angle with respect to the other board. The invention is especially useful in electronic apparatus in which two substrates are mounted to a stationary member such as a chassis and are normally held in the closed state but in which easy access may be had to one or both boards by moving them to the open state.
(2) Description of the Background
In the prior art as illustrated in FIG. 1, in order to mount boards 4 and 6, such as wiring boards, to a stationary board or a fixing board, such as chassis 2, with predetermined distances therebetween, a plurality of securing units 8, 10 as shown in FIG. 1 have been used. However, with these securing units it was difficult to remove the upper board 6 from the board 4 for maintenance work or for repair work. Furthermore, the board 6 normally is electrically connected with the board 4 by lead wires such that, during repair or inspection of the boards, the board 6 must be held by hand so as not to disengage the electric interconnection. The necessity of holding the board 6 by hand diminishes the efficiency of repair and inspection.
In order to overcome the disadvantages mentioned above, another securing unit 12 has been known in the prior art as shown in FIG. 2. Securing unit 12 has hinge means as shown and is used in place of the securing unit 10 as shown in FIG. 1. Although this securing unit 12 allows the board 6 to achieve two different positions when board 6 is moved in the direction of the arrow marked a, i.e., the securing unit 12 permits the board 6 to swing in the direction a, the position of the board 6 after being moved can not be fixed unless it is retained or held by hand, thus making the position of the board 6 unstable and also making the maintenance or repairing work difficult to carry out. This means that the problems encountered in the prior art according to FIG. 1 remain unsolved by the other securing unit 12 according to the prior art of FIG. 2.